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After several weeks' work with @lisai9093, now it's time to post a guide.

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GUIDE:
Intel HD Graphics 5500 on OS X Yosemite 10.10.3

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Before we get started:

The basic idea to make Broadwell's integrated graphics card work does not change.

If you have Intel HD Graphics 5300 or other IGPU models supported by AppleIntelBDWGraphicsFramebuffer.kext, you can try it by yourself.

Detailed framebuffer information and this guide can be found on my blog.
Brief Introduction:

The basic idea to let Intel HD Graphics 5500 work is still injecting AAPL, ig-platform-id.

However, Apple raised the minimum stolen memory in the AppleIntelBDWGraphicsFramebuffer binary of OS X Yosemite 10.10.3.
Kernel panic will happen if the DVMT pre-allocated memory in BIOS settings is lower than 66MB.(based on experimental data; not sure; please correct me if I was wrong.) This is not a big deal for Desktop PCs users, because one can easily change the DVMT pre-allocated memory in BIOS.
But this is catastrophic for laptop users, because
(1) the default value of DVMT pre-allocated memory in laptop BIOS is 32MB.
(2) OEM will not unlock these advanced settings/menus for us.
(3) We can try to modify BIOS but cannot pass the security check during flashing modified BIOS.

In general, if DVMT pre-allocated memory in BIOS settings is less or equal to 96MB, the StolenMemory that could be detected by OS is (DVMT - 32) MB.If DVMT pre-allocated memory in BIOS settings is larger or equal to 128MB, the StolenMemory that could be detected by OS is (DVMT) MB. (equal to the value of DVMT pre-allocated memory)Now let's come back to our main topic, Dedicated Video Memory >=64MB (i.e. DVMT pre-allocated memory >= 96MB) will pass the assertion/kernel panic.

Note that OS X can not boot on some laptops if DVMT pre-allocated memory is >= 128MB.Therefore, if your current DVMT pre-allocated memory size <= 64MB (i.e. Dedicated Video Memory <= 32MB), you can either choose using our patch in STEP 2.1 or changing DVMT pre-allocated setting in STEP 2.2
STEP 2.1: Apply the patch to pass the Stolen Memory assertion.

We need to patch AppleIntelBDWGraphicsFramebuffer binary file.Find 39CF763C and replace it with 39CF773C.

After using this patch, in theory you don't have to change your BIOS settings.
You can try to inject ig-platform-id and see what happens.

If you encounter some problems, try to modify Framebuffer data in AppleIntelBDWGraphicsFramebuffer binary.Detailed information on Broadwell's framebuffer can be found on this page.
STEP 2.2: Using EFI Shell to change DVMT settings in BIOS.

(1) Prepare a bootable USB drive with EFI ShellPrepare a USB stick and format it with FAT32 filesystem.Download this EFI shell and you can find a folder named BOOT after extracting.Copy this BOOT folder to your USB stick.

(2) Dump/Fetch a completed BIOS file.You can use specific BIOS utility to save a copy of your BIOS on Desktop.e.g. For AMI Aptio UEFI BIOS, you can use AMI BIOS Utility.

(3) Extract BIOS Settings from a BIOS file.Download UEFITools from https://github.com/LongSoft/UEFITool/releasesOpen your BIOS file with UEFITools.Find the module labeled with Setup and extract the PE32 image section in this module as a binary file.

Now, you will have a binary file on your Desktop. In my case, I name it Setup.bin.Next, download the Universal IFR Extractor (Windows version only) from http://donovan6000.blogspot.ca/2014/02/universal-ifr-extractor.html or from here: Universal IFR Extractor.exe.Open the Universal IFR Extractor in Windows, open the binary you just extracted from UEFITools and click Extract to save the BIOS settings in plain text format.
Now open the extracted setup IFR.txt and find the keyword "DVMT".And you can find the variable representing DVMT pre-allocated memory and its values.

In this case, DVMT pre-allocated memory's variable is 0x1C3. The value of 96MB is 0x3. Record these two values.Next, restart your computer and boot from the USB drive with EFI Shell.Here, we use setup_var command to change our BIOS settings.

Using FakeSMC 5.3.820 or other 5.x.xxx version will decrease the opportunity to freeze.(Note that please delete CPUSensors.kext from FakeSMC.kext if you get kernel panic related to CPUSensors.kext)Reference and Special Thanks:

Thanks to Rehabman @ tonymacx86 for his advice on garbled screen issue.